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Followers of Shiite cleric Muqtada al-Sadr chant anti-U.S. slogans and wave Iraqi flags as they celebrate the U.S. withdrawal in the Shiite stronghold of Sadr City in Baghdad, Iraq, Feb. 9, 2012.AP Photo

Now that the war is officially over and most U.S. forces have withdrawn, what are the most important takeaways?

This month marks the ninth anniversary of the U.S. invasion of Iraq. Regardless of your views on the wisdom of that decision, it's fair to say that the results were not what most Americans expected. Now that the war is officially over and most U.S. forces have withdrawn, what lessons should Americans (and others) draw from the experience? There are many lessons that one might learn, of course, but here are my Top 10 Lessons from the Iraq War.

Lesson #1: The United States lost.The first and most important lesson of Iraq war is that we didn't win in any meaningful sense of that term. The alleged purpose of the war was eliminating Saddam Hussein's weapons of mass destruction, but it turns out he didn't have any. Oops. Then the rationale shifted to creating a pro-American democracy, but Iraq today is at best a quasi-democracy and far from pro-American. The destruction of Iraq improved Iran's position in the Persian Gulf — which is hardly something the United States intended — and the costs of the war (easily exceeding $1 trillion dollars) are much larger than U.S. leaders anticipated or promised. The war was also a giant distraction, which diverted the Bush administration from other priorities (e.g., Afghanistan) and made the United States much less popular around the world.

This lesson is important because supporters of the war are already marketing a revisionist version. In this counternarrative, the 2007 surge was a huge success (it wasn't, because it failed to produce political reconciliation) and Iraq is now on the road to stable and prosperous democracy. And the costs weren't really that bad. Another variant of this myth is the idea that President George W. Bush and Gen. David Petraeus had "won" the war by 2008, but President Obama then lost it by getting out early. This view ignores the fact that the Bush administration negotiated the 2008 Status of Forces agreement that set the timetable for U.S. withdrawal, and Obama couldn't stay in Iraq once the Iraqi government made it clear it wanted us out.

The danger of this false narrative is obvious: If Americans come to see the war as a success — which it clearly wasn't — they may continue to listen to the advice of its advocates and be more inclined to repeat similar mistakes in the future.